Carbamazepine is practically insoluble
in water and soluble in alcohol. It is a bitter substance
with an unpleasant after-taste. Suspensions are commercially
available, and should be used whenever possible. Carbamazepine
has been reported to be stable for at least 30 days in a variety of formulations
prepared from tablets.1,2 Tegretol®
tablets (not controlled release) disperse easily and rapidly in water. Chewable
tablets are also available.
Carbamazepine oral liquid is available in many countries and should be used
whenever possible.
Formula 1
Carbamazepine 200mg per 5mL |
| |
| Carbamazepine tablets 200mg |
20 |
|
| Syrup |
to 100 |
mL |
| |
|
If the syrup is unpreserved add 0.1% parabens or, providing the pH is 5 or less, 0.1%
sodium benzoate. |
| |
| Expiry: 30
days |
| |
Storage: Refrigerate.
Amber glass bottles and plastic oral syringes used in the study.1
Should be stored in airtight containers to prevent degradation. |
| |
|
Shake Before Use |
| |
|
|
|
NOTES
- The above formula is the simplest but the sugar content may be unacceptable.
Alternative formulations utilising a base of (approximately) syrup 30mL, sorbitol 70% 8mL,
glycerol 2mL, parabens 0.1%, water to 100mL1; or syrup 30mL,
methylcellulose 1% 70mL, preserved with sodium benzoate2 have
been proposed.
- Tegretol® tablets (not controlled release) disperse easily
and rapidly in water.
Chewable tablets are also available.
- The absorption characteristics and bioavaliability of the suspension may be different to that of
the tablet. In the study by Bloomer et al2 the
extent of absorption was similar between tablet and suspension. The suspension produced significantly earlier and higher peak concentrations.
- Carbamazepine suspension should be mixed with an equal volume of diluent (water or normal saline)
before nasogastric administration to minimize adherence of the suspension to the tubing.3
REFERENCES
- Burkart G.J., Hammond R.W., Akers M.J. Stability of extemporaneous suspensions of
carbamazepine.
Am J Hosp Pharm 1981; 38: 1929-31.
- Bloomer D., Dupuis L.L., MacGregor D., Soldin S.J. Palatability and relative
bioavailability of an extemporaneous carbamazepine oral suspension. Clin Pharm 1987;
6: 646-49.
- Clark-Schmidt A.L. Loss of carbamazepine suspension through nasogastric feeding tubes.
Am J Hosp Pharm 1990; 47: 2034-37.
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